A technique, in which two display panels overlap each other and an image is displayed on each display panel based on input image data, has been conventionally proposed to improve contrast of a liquid crystal display device (for example, see Unexamined Japanese Patent Publication No. 2008-191269). Specifically, for example, a color image is displayed on a front-side (observer-side) display panel in two display panels disposed back and forth, and a black-and-white image is displayed on a rear-side (backlight-side) display panel, thereby improving contrast.
However, in the conventional liquid crystal display device, in the case that a number of bits of the input image data is larger than a number of driving bits of the two display panels, it is necessary to display the image while the number of bits of the input image data is decreased, which the number of gradations that can be expressed may decreased.
An object of the present disclosure is to suppress the decrease of the number of gradations that can be expressed in a liquid crystal display device in which a plurality of display panels overlap each other.